Hi all. Just had Grundfos pump head replaced on Saunier Duval F35E Classic as it had seized. BG engineer suggested a Magnaclean. Before he replaced the pump head, he managed to free it up and found that the water surrounding it was discoloured but not to a huge extent. Now new pump head is in, boiler is fine, thankfully. Question is, is it worth my while having the Magnaclean installed? How do I tell if there is corrosion in the system to warrant the installation of a Magnaclean or something similar?